ST10F271Z1T3 datasheet(27/185 Pages) STMICROELECTRONICS

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ST10F271Z1

Internal Flash memory

27/185

5.3

Write operation

The Flash module have one single register interface mapped in the memory space of the

IBUS (0x08 0000 to 0x08 0015). All the operations are enabled through four 16-bit control

registers: Flash Control Register 1-0 High/Low (FCR1H/L-FCR0H/L). Eight other 16-bit

registers are used to store Flash Address and Data for Program operations (FARH/L and

FDR1H/L-FDR0H/L) and Write Operation Error flags (FERH/L). All registers are accessible

with 8 and 16-bit instructions (since operates in 16-bit mode when in read/ write).

Before accessing the IFlash module (and consequently also the Flash register to be used for

program/erasing operations), bit ROMEN in SYSCON register shall be set.

During a Flash write operation any attempt to read the Flash itself, that is under

modification, will output invalid data (software trap 009Bh). This means that the Flash is not

fetchable when a programming operation is active: the write operation commands must be

executed from another memory (internal RAM or external memory), as in ST10F269 device.

In fact, due to IBUS characteristics, it is not possible to perform a write operation on IFlash,

when fetching code from IFlash.

Direct addressing is not allowed for write accesses to IFlash Control Registers.

During a Write operation, when bit LOCK of FCR0 is set, it is forbidden to write into the

Flash Control Registers.

Power supply drop

If during a write operation the internal low voltage supply drops below a certain internal

voltage threshold, any write operation running is suddenly interrupted and the module is

reset to Read mode. At following Power-on, the interrupted Flash write operation must be

repeated.

5.4

5.4.1

Flash control register 0 low

The Flash Control Register 0 Low (FCR0L) together with the Flash Control Register 0 High

(FCR0H) is used to enable and to monitor all the write operations on the IFlash. The user

has no access in write mode to the Test-Flash (B0TF). Besides, Test-Flash block is seen by

the user in Bootstrap Mode only.

FCR0L (0x08 0000)

FCR

Reset Value: 0000h

987

65432

reserved

LOCK

res.

BSY0

res.

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